Removable electrode display device

ABSTRACT

An electroluminescent display device formed by superimposing a first substrate upon a second substrate, forming a cell between the surfaces of the two substrates. A common transparent electrode is deposited on the outside surface of one of the two substrates overlying the entire cell formed by the superimposed substrates. A conductive pattern electrode, having a desired configuration, is placed in intimate contact (e.g., pressure contact) against the outside surface of the other substrate. Information is displayed by applying an alternating voltage of sufficient magnitude and frequency between the two electrodes, resulting in the ignition of an excitable gas contained within the formed cell, the illumination produced corresponding to the configuration of the conductive pattern electrode. The conductive pattern electrode is removable, since it is retained against the outside surface of the cell only by a pressure contact; therefore, the type of information to be displayed can be easily varied simply by removing the conductive pattern electrode and placing another in its place. The various designs of removable electrode patterns which can be employed are endless and can encompass Arabic numerals, alphabetic characters, and other designs.

Elnited States Patent [72] inventor J0hnL..lanning Dayton, Ohio [2 1] Appl. No. 880,676 [22] Filed Nov. 28, 1969 [45] Patented Dec. 21, 1971 [73] Assignee The National Cash Register Company Dayton, Ohio [54] REMOVABLE ELECTRODE DISPLAY DEVICE 5 Claims, 7 Drawing Figs.

[56] References Cited UNITED STATES PATENTS 2,004,577 6/1935 Lebedenko et al. 313/1095 3,497,751 2/1970 Cuilis, Jr 313/1096 Primary Examiner-Raymond F. l-lossfeld Attorneys-Louis A. Kline and Albert L. Sessler, J r,

ABSTRACT: An electroluminescent display device formed by superimposing a first substrate upon a second substrate, forming a cell between the surfaces of the two substrates. A common transparent electrode is deposited on the outside surface of one of the two substrates overlying the entire cell formed by the superimposed substrates. A conductive pattern electrode, having a desired configuration, is placed in intimate contact (e.g., pressure contact) against the outside surface of the other substrate. information is displayed by applying an alternating voltage of sufficient magnitude and frequency between the two electrodes, resulting in the ignition of an excitable gas contained within the formed cell, the illumination produced corresponding to the configuration of the conductive pattern electrode. The conductive pattern electrode is removable, since it is retained against the outside surface of the cell only by a pressure contact; therefore, the type of information to be displayed can be easily varied simply by removing the conductive pattern electrode and placing another in its place. The

. various designs of removable electrode patterns which can be employed are endless and can encompass Arabic numerals, alphabetic characters, and other designs.

31b CHARACTE'R SOURCE SELECTOR PATENTED DECZI l97| 29, 54

SHEET 1 OF 2 CHARACTER SELECTOR A c SOURCE TO ALL SOURCE INVENTOR JOHN L. JANNING HIS ATTORNEYS PATENTED M21 IQYI SHEET 2 OF 2 INVENTOR JOHN L.JANNING mm HIIHLM HIS ATTORNEYS BACKGROUND OF THE INVENTION The present invention relates to an electroluminescent display cell having a permanent electrode and a movable electrode.

Electroluminescent display devices which produce illumination corresponding to a particular pattern upon the application of an electrical potential across the electroluminescent display device are well known. Devices of this type are exemplified in U.S. Pat. No. 3,127,535, issued Mar. 31, 1964, on the application of Harold T. Westerheim, and in British Pats. Nos. 1,161,832 and 1,161,833.

A continuing problem, applicable to most electroluminescent display devices, has been the inability to provide a structure that can be readily and reproducibly fabricated. Another expensive problem found in the prior art devices is the fact that the entire display device must be replaced upon the deterioration of the electrodes, a problem which is particularly prevalent when the electrodes are internal to the cell. These and other undesirable features found in most prior art devices have been eliminated in the instant invention.

It is therefore an object of the present invention to provide a novel electroluminescent display cell which permits the easy replacement of the electrode which determines the design of the configuration to be displayed, a feature which also obviates the necessity of replacing the entire display cell in the event of electrode failure.

Another object of the invention is to provide an electroluminescent display cell in which the type of information to be displayed is not pennanently affixed to the cell, thereby resulting in a display cell capable of being utilized for displaying different types and kinds of information.

A further object of the invention is to provide a structure which is capable of easy manufacture.

Display cells fabricated in accordance with the teachings of this invention allow for automated production, since no special cavities, or designs or any sort, need be placed on the cell's wall surfaces for outlining the character to be displayed.

SUMMARY OF THE INVENTION This invention permits the display of variable information, since the information to be displayed is not restricted to the display cell.

One form of the invention features a display cell formed by the assembly of two elements -i.e., two transparent flat plates the plates assembled in such a manner that there is formed between the two inner faces a cell for the containment of a gaseous medium. One exterior side of the assembly serves as the front side; i.e., the side which will be exposed to a viewer. A transparent common electrode is deposited on the front side, completely overlying the cell formed within the assembly. On the other exterior side of the assemblyi.e., the rear side-is placed a movable character electrode. The character electrode may be an insulating card containing conductive character electrodes with the desired design configuration. The movable character electrode is affixed to the rear side of the display cell by conventional means, such as spring means, which also facilitates the removal of the character electrode. The illumination necessary for viewing the character to be displayed is provided by the application of an alternating potential between the common electrode and the movable character electrode. This causes ignition to occur within the gas-containing cell, thus providing illumination conforming to the configuration of the movable electrode.

A second form of the invention features a display cell of tubular construction, resulting in a display cell having somewhat the shape of a conventional vacuum tube. This form of the invention utilizes a transparent electrode deposited on the exterior surface of the outside tube, which is the surface exposed to a viewer. The movable electrode may be an internal electrode plug, or may take the form of copper-clad electrodes on Mylar film, or may be any other material, having electrodes thereon, which may be inserted within the inside opening of the tubular cell.

Both forms of the invention are extremely versatile, in that the information to be displayed can be changed simply by the replacement of the movable electrode. The invention also lessens the occurrence of cell replacement; e.g., if any spots were to occur on the glass plates, the problem could be obviated simply by moving the movable electrode to a clear spot on the glass. Defective cells are easily replaced, since it is necessary only to replace the glass housing, leaving the character electrodes intact.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by referring to the following drawings.

FIG. I is an exploded isometric view of one embodiment of the display assembly in accordance with the invention.

FIG. 2 is an isometric view of another form of the embodiment shown in FIG. 1.

FIG. 3 is a front view of the display assembly in use with a circular electrode pattem-containing disc.

FIG. 3a is a cross-sectional view taken along the line 30 of FIG. 3 to show more details of a conventional means for rotating the disc.

FIG. 4 is a isometric view of still another form of the invention.

FIG. 5 is a plan view of the embodiment illustrated in FIG. 4.

FIG. 6 illustrates the different form of construction that the embodiment in FIG. 4 can take.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the invention, reference is now made to FIG. I, which illustrates one form of the invention. The display assembly 20 is composed of first, second, and third plates, 21 22, and 23, each having first and second sides, the first sides being those sides facing the transparent electrode 25. The plates in the completed structure are held together by conventional means such as glass solder or glass cement, thereby resulting in an airtight structure. The plate 22 is nothing more than a spacer, having a central opening therethrough, spacing the plate 21 from the plate 23, and also forming a uniform cell within the assembled structure. The plate 23 has a hole formed therein for the purpose of receiving a conduit 24. The conduit 24 provides means by which the cell, formed between the plates 21 and 23, is evacuated of air, and also provides the means by which the cell is filled with an electroluminescent material-i.e., gas-after which the conduit 24 is sealed. The first plate, 21, has attached to its outside surface (first side) a transparent conductive electrode 25 of a material such as cadmium oxide, tin oxide, thin gold, or any other suitable conductive material. The transparent conductive electrode 25 may be deposited on the glass surface by conventional methods such as metal deposition or other wellknown coating techniques. The electrode 25 serves as the common electrode for the display of FIG. 1.

Two pressure-applying nonconducting elements (leaf springs), which are cemented onto the outside surface (second side) of the rear plate 23, provide sufficient pressure to retain a pattern electrode card 30 in intimate contact with the outside surface (second side) of the glass plate 23. Electrodes 32 having a particular configuration are coated on or imbedded in the insulating card 30, each electrode being connected to its own input terminal, the terminals shown generally at 31. Although the electrodes 32 in FIG. I are shown as a seven-bar matrix, it is apparent that the electrode pattern could have any desired configuration, such as numeric, alphabetic, alphanumeric, etc., the only requirement being that the pattern electrodes overlie the gas cell. The electrodes 32 are connected to a source 310 of AC potential via a conventional character selector 31b; and the transparent conductive electrode 25 is also connected to the AC source 31a.

It can be seen that the transparent electrode 25 is capacitively coupled to the cell formed within the glass structure, due to the external positioning of the electrode 25, thereby being separated from the cell by the glass dielectric forming the structure. Similarly, the electrodes 32 are also capacitively coupled to the cell.

Looking at the display 60 of FIG. 2, it can be seen that the embodiment of FIG. 1 can take another form. In FIG. 2, a hermetic chamber is formed by the two substrates, the plates 61 and 62. The chambers can be conventionally etched on the second side of the plate 61 and on the first side of the plate 62. When assembled and sealed, the chambers on the plates 61 and 62 are in full registry, thereby defining a cell capable of maintaining a pressurized gas. The gas is introduced into the structure through a conduit 69. If desired, the chamber need be formed on only one of the two plates. A transparent film electrode 63, which functions as the common electrode for the display device 60, is deposited conventionally on the outside surface (first side) of the plate 61. Electrodes 65 and 66 are coated on or imbedded in an insulating card 64, each electrode connected to an input terminal 67. The electrode character card 64 is held against the outside surface (second side) of the plate 62 by springs 68, thereby placing the character electrodes 65 and 66 in intimate contact with the plate 62. The electrodes 63, 65, and 66 may be energized in the same manner as those shown in FIG. 1.

In operation, the display devices of FIGS. 1 and 2 are similar. Therefore, only the operation of the embodiment shown in FIG. 1 need be described. The movable insulating card 30, containing the character electrodes 32, is placed in contact with the outside surface of the rear plate 23. Application of an alternating potential between selected terminals 31 of the character electrodes 32 and the common transparent electrode 25 causes an electron multiplication process to occur within the cell. This multiplication process proceeds until breakdown occurs; i.e., a gaseous discharge occurs within the cell. The ionization will be limited and will conform to the configuration of the character electrodes. The parameters involved in producing the ionization for the desired illumination include the potential applied across the cell, the distance between the electrodes 25 and 32, and the pressure of the gas contained in the cell. The ionization provides the illumination conforming to the shape of the electrode patterns, necessary for viewing by an observer. The ionization occurring within the cell also provides the display cell with a memory, because the ionization occurring within the cell results in the deposition of charged particles on the inner cell wall surfaces of the plates 21 and 23. Positive charges are deposited on the inner cell wall surface capacitively coupled to the electrode to which negative potential is being applied, and electrons are deposited on the inner cell wall surface capacitively coupled to the electrode to which a positive potential is being applied. These charges are trapped on the cell walls because of the capacitive coupling effect exerted by the glass cell walls. It can then be seen that the deposited wall charge has a polarity which is opposite to that of the potential initiating the ionization. Therefore, on the succeeding reverse cycle, the wall charge will be additive to the applied potential, thereby insuring ignition on the succeeding reverse cycle and also lowering the criticality of maintaining the applied potential at one specific value. In other words, after the first ionization, the voltage necessary to sustain the ignition can be of a magnitude which is equal to the original applied potential less the wall charge. By proper selection of the desired character electrodes, any type of character can be displayed.

FIG. 3 illustrates means by which information may serially be displayed. Electrodes 33 are deposited on a circular insulating disc 34, the disc being rotatably mounted on a shaft 35, which can be rotated by any conventional stepping mechanism. The insulating disc 34 is resilient and applies pressure against the outside surface of the rear plate 23,. thereby retaining the electrode patterns in intimate contact with the glass surface. Rotating contacts are connected to each character and are located on the rear surface of the assembly 20. The rotating contacts may be connected to an electrical source by any conventional means.

One such conventional means is shown in FIG. 30. Each electrode (like 33) is provided with an electrical contact 80, which is suitably secured to the rear surface of the disc 34 as shown, and a conductor 82, passing through the disc, connects the electrode (like 33) with its associated contact 80. A stationary electrode 84, connected to an AC source, completes the electrical connection to the selected electrode when the electrode (like 33) is positioned in the topmost position (like the character 3 in FIG. 3), where the character contacts the assembly 20.

A conventional stepping mechanism for rotating the disc 34 is shown in FIGS. 3 and 3a. The disc 34 has teeth 90 on a portion of its periphery, which teeth are driven by a driving gear 92 associated with a conventional stepping motor 94. The motor 94 rotates the disc 34 so as to position the selected character to the topmost position (like the character 3 shown in FIG. 3), where the selected character contacts the assembly 20, and its associated contact engages the stationary contact 84 to energize the assembly 20. A conventional character select means (not shown) may be used for energizing the stepping motor 94.

Illustrated in FIG. 4 is a single character display 3Q featuring tubular construction. The display cell 39 is fabricated from two glass tubes 41 and 42. The tube 42, having an outside diameter less than that of the tube 41, is placed inside of the tube 41, the tubes being in concentric relationship with respect to each other. The concentric relationship is further insured by spacer tips 51. The tube 41 is open at both ends, and the tube 42 is closed at one end and open at the other. One open end of the tube 41 is sealed to the exterior surface of the tube 42, as shown at 420 in FIG. 5, thereby forming an annular chamber between the inside wall of the outside tube 41 and the outside wall of the inside tube 42. Evacuation means are connected to the remaining open end of the tube M. The chamber is evacuated of air and is then filled with an electroluminescent material such as gas. The tube 41 is then sealed, resulting in the formation of a tip 43.

The outside of the tube 41 is coated with a transparent conductive common electrode 40 over its entire cylindrical surface. The transparent electrode can be of a material such as cadmium oxide, tin oxide, thin gold, or any other material which can be deposited and which will adhere to the outside glass surface of the tube 41. Coating of the electrode can be accomplished by conventional methods such as metal deposition techniques. A metallic band 50, such as gold, is positioned over the transparent conductor at the lower end of the tube 41, the band being utilized to insure a better contact with the spring-loaded contact 48. The contact 48 and the pins 47 are connected to an energizing source like the one shown in FIG. 1.

The movable electrodes for the display are on a separate substrate 44, which may be in the form of a plug. As one skilled in the art can see, there are many possible ways to fabricate such an electrode plug, such as copper-clad electrodes on Mylar, one piece molded plugs with electrodes potted in place, and thin-film electrodes on various flexible substrate forms. In order to complete the display assembly, the electrode plug is inserted into an opening 45 of the tube 42. The outer dimensions are such that the plug 44 will place the electrode patterns 46 into contact with the inside glass surface of the tube 42. By way of example only, the electrode pattern on the plug 44 is shown to consist of a seven-bar matrix in which leads are brought out to the pin electrodes 47 for insertion into a suitable socket. The electrodes 46 can consist of any suitable material, such as gold, and may be deposited on the plug by any conventional method.

FIG. 6 illustrates the fact that the device of FIG. 4 need not be restricted to tubular construction. The device 70 is fabricated from two rectangular members 71 and 72. The member 71 is placed inside the member 72, thereby forming a chamber between the inside surface of the tube 72 and the outside surface of the member 71. The member 71 is closed at one end and open at the other; the member 72 is open at both ends. The two open ends are sealed together, and evacuation means are connected to the open end of the member 72 for the evacuation of air from the chamber and also for the introduction of an electroluminescent material into the chamber, after which the open end of the member 72 is closed. A rectangular card 73, containing character electrodes 74, is placed in intimate contact with the inside surface of the member 71. Each electrode 74 is connected to its own input terminal 75 for connection to a suitable energizing source. Uniform spacing between the members 71 and 72 is insured by spacer tips 76. The outer surface of the member 72 has a transparent conductor coating thereon (as was done with the FIG. 4 embodiment), and a metallic band 77 is positioned over the coating to insure a good contact with an energizing source like the one shown in FIG. 1. Although only one character 74 is shown, a plurality of characters, one on each side surface of the card 73, could be displayed.

The operation of the embodiments shown in FIGS. 4 and 6 is similar to that shown in FIG. 1, in that, when voltage of a sufficient magnitude is applied between selected character electrodes and the common transparent electrode 40, (as shown in the FIG. 1 embodiment) a discharge will be created in the chamber in the area immediately adjacent to the selected character electrodes. The discharge will be limited to the area adjacent to the selected electrodes by the selection of suitable applied energizing potential, gas pressure, and distance between common and character electrodes.

In order to aid those skilled in the art in the practice of the present invention, the following information is given by way of exemplification only. In the embodiment illustrated in FIG. 6, the spacing between the tubes was 0.010 inch and can range up to 0.015 inch, with a wall thickness of approximately 0.030 inch. The gas mixture consisted of 99.7 percent neon, 0.2 percent nitrogen, and 0.1 percent argon and was at a pressure of 140 millimeters of mercury. The operating voltage was 475 volts AC, having two-microsecond pulses with microseconds spacing. Reducing the tube wall thickness reduces the required operating voltage significantly; or, inversely, increasing the tube wall thickness increases the operating voltage.

What is claimed is:

l. A low-cost gaseous electroluminescent device comprismg:

first and second transparent elements, each having an inside surface and an outside surface, with said inside surfaces facing each other and being spaced apart a distance of approximately 0.010 inch;

means for hermetically sealing said elements to form a chamber therebetween;

an ionizable gas filling said chamber;

a continuous coating of transparent, electrically conductive material contacting the outside surface of the first element to form a coating electrode thereon;

a movable character electrode means;

means for positioning said character electrode means to contact the outside surface of said second element; and a source of AC potential connected to said character electrode means and said coating electrode to ionize said gas to produce an illumination conforming to the shape of the character electrode means.

2. The device as claimed in claim 1 in which said means for positioning said character electrode means comprises:

a disc made of electrically insulating material and rotatably mounted on a shaft; and

drive means for rotating said disc;

said character electrode means comprising: conductor character elements located on one face of said disc and means for connecting said elements to said source of AC Potential;

said disc being positioned relative to the outside surface of the second transparent element so that a selected character element on said disc will be moved by said drive means to contact said outside surface of the second transparent element and thereby ionize said gas to produce an illumination conforming to the shape of the selected character element.

3. The device as claimed in claim 1 in which said movable character electrode means comprises:

a flat planar insulating card having character-forming electrodes on one face thereof, with said electrodes being connected to said source of AC potential;

said means for positioning said character electrode means being holding means (like springs) for holding said card with the face having said character-forming electrodes thereon against the outside surface of the second transparent element to ionize the gas to produce an illumination conforming to the shape of the charactcr-fonning electrodes which are connected to the source of AC potential.

4. The device as claimed in claim 1 in which said first and second transparent elements are first and second tubes with each tube having one closed end and one open end, said second tube being smaller in diameter than the first tube and placed within the first tube in concentric relationship therewith, with said open ends being aligned and sealed together to form said chamber, with the inside surface of the first tube and the outside surface of the second tube forming the inside surfaces of said chamber;

said movable character electrode means being positioned inside said second tube with said electrode means in contact with the inside surface of the second tube.

5. The device as claimed in claim 1 in which said first and second transparent elements are made of glass having a wall thickness of approximately 0.030 inch;

said gas being composed of more than 99 percent neon and less than 1 percent of nitrogen and argon;

said source of AC potential being approximately 450 volts having pulses of two microseconds duration with fifteen microseconds duration between successive pulses.

t i t t 

1. A low-cost gaseous electroluminescent device comprising: first and second transparent elements, each having an inside surface and an outside surface, with said inside surfaces facing each other and being spaced apart a distance of approximately 0.010 inch; means for hermetically sealing said elements to form a chamber therebetween; an ionizable gas filling said chamber; a continuous coating of transparent, electrically conductive material contacting the outside surface of the first element to form a coating electrode thereon; a movable character electrode means; means for positioning said character electrode means to contact the outside surface of said second element; and a source of AC potential connected to said character electrode means and said coating electrode to ionize said gas to produce an illumination conforming to the shape of the character electrode means.
 2. The device as claimed in claim 1 in which said means for positioning said character electrode means comprises: a disc made of electrically insulating material and rotatably mounted on a shaft; and drive means for rotating said disc; said character electrode means comprising: conductor character elements located on one face of said disc and means for connecting said elements to said source of AC potential; said disc being positioned relative to the outside surface of the second transparent element so that a selected character element on said disc will be moved by said drive means to contact said outside surface of the second transparent element and thereby ionize said gas to produce an illumination conforming to the shape of the selected character element.
 3. The device as claimed in claim 1 in which said movable character electrode means comprises: a flat planar insulating card having character-forming electrodes on one face thereof, with said electrodes being connected to said source of AC potential; said means for positioning said character electrode means being holding means (like springs) for holding said card with the face having said character-forming electrodes thereon against the outside surface of the second transparent element to ionize the gas to produce an illumination conforming to the shape of the character-forming electrodes which are connected to the source of AC potential.
 4. The device as claimed in claim 1 in which said first and second transparent elements are first and second tubes with each tube having one closed end and one open end, said second tube being smaller in diameter than the first tube and placed within the first tube in concentric relationship therewith, with said open ends being aligned and sealed together to form said chamber, with the inside surface of the first tube and the outside surface of the second tube forming the inside surfaces of said chamber; said movable character electrode means being positioned inside said second tube with said electrode meanS in contact with the inside surface of the second tube.
 5. The device as claimed in claim 1 in which said first and second transparent elements are made of glass having a wall thickness of approximately 0.030 inch; said gas being composed of more than 99 percent neon and less than 1 percent of nitrogen and argon; said source of AC potential being approximately 450 volts having pulses of two microseconds'' duration with fifteen microseconds'' duration between successive pulses. 